Firing Systems

Calciner Firing Systems

The introduction of the calciner transformed the cement production process. Short kilns and tall preheater towers replaced long kilns; a change that dramatically improved process efficiency. But it also came with a challenge. Calciner temperatures are much lower than those in the kiln – and this posed a conundrum for calciner burner design. How do you still achieve fast ignition and complete combustion, while avoiding hot spots that damage the refractory? It’s that challenge that our calciner firing systems are designed to solve.

Calciner Firing Systems

Pulverized solid fuels? Gas-fired? Fuel flexibility? Whatever your fuel situation, we can engineer a firing system to suit your needs.

Calciner Firing Systems




For pulverized solid fuels

The Pyrobox® is a simple but smart solution. It combines the typical raw meal inlet box with a burner designed to fire solid pulverized fuels (coal, lignite, petcoke, biomass). As the preheated raw meal is fed through the Pyrobox®, it mixes with the fuel to create optimal conditions for direct heat transfer and calcination of the raw meal.

The use of direct heat transfer from fuel to raw meal means there is no open flame in the calciner, which helps to avoid temperature fluctuations and hotspots. This design ensures direct heat transfer and even combustion conditions, reduces temperature peaks and improves the energy efficiency of the process.

Finally, an adjustable and replaceable dispersion plate inside the Pyrobox® ensures the best possible distribution of raw meal into the calciner. There is also no primary air demand (and therefore no fan), reducing electricity consumption and minimizing the introduction of false air compared to traditional burners.


Efficient, flexible and easily retrofitted

Direct heat transfer offers the highest energy efficiency. It’s the major benefit of the Pyrobox®. But it’s not the only one. The steady temperature profile reduces wear on the refractory and the production of NOX. And the mixing of fuel and hot raw meal improves ignition, even of more challenging fuels, such as petcoke.

The design is simple but elegant. No fan not only means no electricity consumption but also no fan maintenance. In fact, the Pyrobox® has pretty minimal maintenance requirements all round.

Calciner Firing Systems

Gas Ring Burner


Gas Ring Burner

Great modularity

Our modular gas ring burners – as the name suggests – comprise a ring duct, onto which several burners are mounted. It’s usually located near the raw meal inlet box of the second lowest cyclone in the preheater tower and is designed to burn a range of gaseous fuels.

Fuel is injected directly through a nozzle system into the calciner, eliminating the need for primary air (and therefore false air leakage). Multiple burners meanwhile ensure ideal mixing of fuel and calciner gases, creating a uniform temperature profile in the calciner and ideal conditions for efficient direct heat transfer.

Each burner can also be controlled individually to optimize fuel flow.

Gas Ring Burner

Highest energy efficiency in a simple package

Utilizing direct heat transfer and eliminating the need for (cold) primary air injection means our gas ring burners offer the highest levels of energy efficiency. And the uniform temperature profile created helps remove the risk of hot spots, improving refractory lifetime and reducing NOX production.

It’s also pretty flexible. You can use any gaseous fuel, including alternative fuels such as biogas, lean gases and hydrogen. Moreover, we can completely customize it to your capacity and heat input needs by adding more sections to the ring duct and more burners, as required. Which makes is a good retrofit option, even for third-party systems.

Maintenance is made easier too. The refractory lasts longer before needing to be replaced – and there is no fan maintenance (because here also, no fan is required)! Add all these together and you have a gas burner system that can meet whatever process requirements you can throw at it.

Calciner Firing Systems

Humboldt Combustion Burner

Humboldt Combustion Burner

HCB for a variety of fuels and applications

Alternative fuels are good from a sustainability point of view – but can be hard to handle and hard to ignite. Which is a problem for a fuel. The Humboldt Combustion Burner is our solution to these challenges.

Fitted as standard to KHD Combustion Chambers or Pyroincinerators – both of which are designed to facilitate the use of coarser alternative fuels – fuel is mechanically fed into the HCB, drastically reducing false air leakage and the risk of blockages. Meanwhile, wear liners along the conveying duct ensure long lifetime and simpler maintenance.

To facilitate ignition, a conical burner seat redirects heat back onto the base of the flame. The insertion depth of the burner can also be adjusted to optimize the ignition point. And if ever combustion conditions need augmenting – e.g., to speed up calciner heat-up – the HCB can fire additional fuels, such as coal dust, gas or liquid fuels.

Discover more about how KHD technologies are reducing the environmental impact of cement on our Clean Solutions page.

Humboldt Combustion Burner

Taking the headache out of alternative fuels

With its ability to more-efficiently fire coarse alternative fuels, the HCB is an important supporting technology in helping the cement industry reduce its environmental footprint – as well as take advantage of a wider range of available fuels without committing to costly preparation steps.

You don’t need a KHD calciner to take advantage either. The HCB is suitable for all alternative fuel calciner systems that allow for vertical installation of the burner.


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